• Journal of Powder Materials
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• v.26 no.6
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• pp.528-538
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• 2019

The transition from "More-of-Less" markets (economies of scale) to "Less-of-More" markets (economies of scope) is supported by advances of disruptive manufacturing and reconfigurable-supply-chain management technologies. With the prevalence of cyber-physical manufacturing systems, additive manufacturing technology is of great impact on industry, the economy, and society. Traditionally, backbone structures are built via bottom-up manufacturing with either pre-fabricated building blocks such as bricks or with layer-by-layer concrete casting such as climbing form-work casting. In both cases, the design selection is limited by form-work design and cost. Accordingly, the tool-less building of architecture with high design freedom is attractive. In the present study, we review the technological trends of additive manufacturing for construction-scale additive manufacturing in particular. The rapid tooling of patterns or molds and rapid manufacturing of construction parts or whole structures is extensively explored through uncertainties from technology. The future regulation still has drawbacks in the adoption of additive manufacturing in construction industries.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.9
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• pp.58-63
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• 2009

Silicon carbide (SiC) has been used for many engineering applications because of their high strength at high temperatures and high resistances to chemical degradation. SiC is very useful especially for a glass lens mold whose components demanded to the machining with good surface finish and low surface damage. The performance and reliability of optical components are strongly influenced by the surface damage of SiC during grinding process. Therefore, the severe process condition optimization shall be necessary for the highly qualified SiC glass lens mold. Usually the major form of damage in grinding of SiC is a crack occurs at surface and subsurface. The energy introduced in the layers close to the surface leads to the formation of these cracks. The experimental studies have been carried out to get optimum conditions for grinding of silicon carbide. To get the required qualified surface finish in grinding of SiC, the selection of type of the wheel is also important. Grinding processes of sintered SiC work-pieces is carried out with varying wheel type, depth of cut and feed using diamond wheel. The machining result of the surface roughness and the number of flaws, have been analyzed by use of surface profilers and SEM.

• 전기의세계
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• v.49 no.9
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• pp.9-16
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• 2000

A receding horizon $H_{\infty}$ predictive control method is derived by solving a min-max problem in non-recursive forms. The min-max cost index is converted to a quadratic form which for systems with input saturation can be minimized using QP. Through the use of closed-loop prediction the prediction of states the use of closed-loop prediction the prediction of states in the presence of disturbances are made non-conservative and it become possible to get a tighter $H_{\infty}$ norm bound. Stability conditions and $H_{\infty}$ norm bounds on disturbance rejection are obtained in infinite horizon sence. Polyhedral types of feasible sets for sets and disturbances are adopted to deal with the input constraints. The weight selection procedures are given in terms of LMIs and the algorithm is formulated so that it can be solved via QP. This work is a modified version of an earlier work which was based on ellipsoidal type feasible sets[15].

• Journal of the Korea Institute of Building Construction
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• v.10 no.4
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• pp.49-57
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• 2010

Selecting an appropriate formwork to fit the construction of a high-rise building is an important factor that can influence the success or failure of a construction. Currently, however, the reality is that in domestic high-rise building construction, the selection of an appropriate formwork with consideration of the characteristics of the formwork has not been done in a reasonable manner. To select formwork in a systematic and reasonable fashion, comprehensive consideration is required that must not only include the aspect of construction costs, but also air, quality, safety, and environmental issues. Therefore, this study aims to rationalize the selection process of formwork by applying the scientific method of Analytic Hierarchy Process (AHP) to the selection process of formwork, in terms of construction costs, quality and safety. To do this, the researcher investigated the current status of formwork being used in high-rise residential building construction. Then, based on the results of this investigation, the researcher selected an alternative for the formwork, and taking construction experts as the subjects of this study, conducted a survey on the applicability of the formwork as well as the priority of management thereof when selecting formwork. It is judged that the results of this research will contribute a more scientific and reasonable decision-making process than the existing non-scientific method in selecting formwork for high-rise residential building construction.

• Korean Journal of Construction Engineering and Management
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• v.15 no.3
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• pp.38-46
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• 2014

The Global's top five Design Firms selected from BauNetz a German architectural magazine in 2007 designed free form building design which was 25% of the overall design by 2006-2010. Free form building is a landmark of the city and the country so its social and economic impacts are very large. In case of Korea, free form buildings such as Tribowl in Incheon, KINTEX Exhibition hall 2 and Dongdaemun Design Plaza have increased. However, those the increase in design trends and, the needs due to the lack of free form building design and construction management experience, free form building projects can't be expected to profitability and have a number of problems after completion. Especially, there are many excessive quality problems and the rising cost due to design changes frequently and lack of experience and data. Thus an initial plan regardless of considering of free form building's characteristics can be a huge risk because of the difference with the plan and actual projects, yet there aren't free form building project's performance data and case studies related to productivity. In this study, through selection of low-construction productivity works and an analysis of the work process and productivity data, hope to propose an actual field productivity of free form building and the ways to improve productivity.

• KIEAE Journal
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• v.10 no.6
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• pp.115-121
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• 2010

This paper is an outgrowth of many years of practicing real interior work projects and one of my responses to the question not only about the actual dimension of interior work surface but also about the classification of contemporary finishing materials in basic interior project of high-rise apartment houses. For this purpose, 8 conventional apartment units which are already-built or designed have been surveyed and the results are interpreted in the form of proportion of space and finishes. The data can be applied to make up a schematic design in the selection of environment-friendly interior works and assessment of the degree of sustainability. For further study, the basic data provided here can be used as an index to differentiate the occupants' desire toward green interior design for their own apartment spaces, comparing to the conventional interior work in the Korean market. Not surprisingly, wall paper is dominated to make the interior surface in apartment houses. In the percentile of the utilization of finishing materials, wood-flooring and coating materials like wet paint also ranked at the upper position.

• Journal of Korean Library and Information Science Society
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• v.29
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• pp.65-103
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• 1998

This study aims to examine both the theoretical framework and practical method for the building a subject-oriented collection of information resources form Internet. Through the study, a few conclusions as well as a suggestion were derived. 1. Conclusions : (1) The continuous learning and studying by the librarians working in the information society is required in order that they could have a broader recognition of the existence of various resources from Internet by subject, and that they could be armed with a greater ability to evaluate for the information filtering. (2) The use of a subject directory to collect needed information resources form Internet revealed the necessity for going through many steps linked by hierarchical indexes till arriving at the desired information, and accordingly the great time was needed to conduct the work. (3) In case of using various search engines, since the output of the relevant information largely depends on the adequate defining of the topic, the right selection of search terms and the accurate methods of inputting the keywords, systematic organization of the resources is not simple and easy. The classifying work of collected resources for the topic into the broader categories differs from that of the resources form other topics, for example, psychology, because of the idiosyncrasy of the contents of the each topic. (4) As one method to provide more revolutionary value-added service using Internet, it is necessary for the librarians to learn the skills to build the Web resource pages of subject-oriented collection of information resources from Internet on the specific subject. 2. A suggestion : Since the study did not complete the collection and organization of the information resources from the Internet on this topic, the remaining research and task should be the thorough collection of resources and the building the Web resource pages consisting of interconnecting links of indexes by spending greater time.

• Korean Journal of Construction Engineering and Management
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• v.17 no.2
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• pp.135-145
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• 2016

In Korea, a series of noise-reduced aluminum forms are being recently used in apartment housing construction. However, their complicated and time-consuming work processes, and the noise which is still generated due to the inherent property of aluminum when especially installing and dismantling them have been pointed out as a problem to be certainly solved for increasing their practical use in construction sites. The primary objectives of this study are proposing an optimal conceptual design of a newly designed noise-reduced aluminum form and verifying the technical feasibility by conducting a working mock-up drive experiment. Thus, conventional noise-reduced aluminum forms have been analyzed and three conceptual designs of a newly noise-reduced aluminum forms have been deducted. AHP has been applied to a survey data collected by interviewing field experts. A trade-off analysis results have shown that 'Noise-reduced System Aluminum Form with a Drop-down Floor Post and Adaptive Beam' the highest weights of safety(0.52), work convenience(0.54) and thus selected. The suggested conceptual design in this study improved problems of conventional system aluminum forms. It is also expected that the suggested design will be used as a reliable guideline for the actual development of an aluminum form that ensures noise-reduce, work convenience and labor safety.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39B no.11
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• pp.803-809
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• 2014

In this paper, we investigate physical layer security in a cooperative cognitive radio networks (CRN) with a relay selection in the presence of a primary user and an eavesdropper. To protect the CRN from wiretapping by the eavesdropper, we propose employing an opportunistic relay selection scheme and multiple antennas at the destination that work based on the availability of channel state information at the receivers. Under these configurations, we derive an exact closed-form expression for the secrecy outage probability of the CRN, and also derive an asymptotic probability. Numerical results will be presented to verify the analysis.

• The Journal of Information Technology and Database
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• v.7 no.2
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• pp.47-59
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• 2000

In this paper, we analyze the applicability of a general optimization algorithm to a database optimization problem. The index selection problem Is the problem to choose a set of indexes for a database in a way that the cost to process queries in the given workload is minimized subject to a given storage space restriction for storing indexes. The problem is well known in database research fields, and many optimization and/or heuristic algorithms have been proposed. Our work differs from previous research in that we formalize the problem in the form of non-linear Integer Programming model, and investigate the feasibility and applicability of a general purpose optimization algorithm, called OPBDP, through experiments. We implemented algorithms to generate workload data sets and problem instances for the experiment. The OPBDP algorithm, which is a non-linear 0-1 Integer Programming problem solver based on Davis-Putnam method, worked generally well for our problem formulation. The experiment result showed various performance characteristics depending on the types of decision variables, variable navigation methods and ocher algorithm parameters, and indicates the need of further study on the exploitation of the general purpose optimization techniques for the optimization problems in database area.